The invention relates to an electrical switch gear apparatus, in particular a switch, equipped with at least one pair of separable contact means comprising a first long, slender contact means defining a longitudinal axis and a first and a second ends and having a contact zone on the same side as its first end and an electrical connection zone on the same side as its second end, and a second contact means having a contact zone, the pair of contact means being able to take a closed position in which the two contact means are in contact with one another via their respective contact zones, and an open position in which the two contact means are separated from one another, the opening movement being such that when separation of the two contact means takes place, the speed of the contact zone of the second contact means with respect to the first contact means has a predominant component following an axis perpendicular to the longitudinal axis of the first contact means.
A conventional apparatus of this type is represented for example purposes in FIG. 1. A pole 10 of this apparatus comprises a movable contact means 12, a stationary contact means 14 and an arc extinguishing chamber 16 with separators 18. The stationary contact means 14 comprise a contact zone 20 and a connection zone 22.
Likewise, the movable contact means 12 comprise a contact zone 24 and a connection zone 26. The two means 12, 14 are long and slender and placed in the extension of one another so that in the closed position the current lines 28 flowing between the two connection zones are appreciably loop-free. The movement of the movable contact means when opening takes place follows a direction 30 appreciably perpendicular to the direction of the current lines before opening, so that the electrical arc 32 which arises between the contact zones 20, 24 at the level of the last contact points A, B tends to flee towards the ends of the two contact means, at A' and B' , according to the directions 34, 36. In particular, the foot of the arc is directed towards A' in the direction 34 opposite to the arc extinguishing chamber 16. This movement is not favorable to entry of the arc into the chamber. In conventional switch gear, the ionization generated by the arc at the beginning of opening is sufficient for a new arc breakdown to take place according to a line of smaller distance between the two contacts. The geometry of the pole is such that this line is situated close to the chamber and passes via the free end B' of the movable contact means 12, so that the new arc extends in the latter, whereas the first arc is extinguished.
This operating mode is satisfactory when the required performances are low, with overload currents lower for example than 6 I.sub.n, I.sub.n being the nominal current. It is no is longer suitable when higher performances are sought for, for example with overload currents reaching 8 I.sub.n, or when closing and opening cycles on overload are required. The breaking time with such a device is in fact long, and the stagnation of the arc at the end of the contact means causes excessive erosion of the contact zones when the overload currents are high.
It is moreover known that it is possible to direct the arc to the chamber by adopting a stationary contact means having a U shape. However, such a configuration, commonly used for circuit breakers, results in large dimensions.